NavList:

Hi Josh

Interesting question in a broad sense – but the answer cannot be quantified in the terms you have laid out and likely will create some interesting answers – so I will be brief at the first attempt of an answer.

From the internet – GPS – ‘a satellite-based navigation system that provides precise location, velocity, and time synchronization to users anywhere on Earth in any weather’ and though I have been out of the air force since well before GPS – as accurate as an overhead a point of geography, a radar fix etc.

Whereas astro is navigational aid – it could never give you a fix and at best a single position line and depending on what service you were in ‘degrees of error’ around that line. i.e. you could never say ‘here I am’, ‘this is where I am at’. …….. but take another astro shot at say 120 degs removed and a 3rd shot further removed by 120 deg and you got a ‘fix’  - however, a fix from an astro shot x3 is vastly different from a fix from a GPS.

But, the 3-star fix, typically gives a ‘cocked hat’ and IF???? - your shots are accurate ( and here lies the very essence of your question Josh)  - if they were all equally accurate then the ‘cocked hat’ would be small. But even then, all things being good and all errors possible in an astro shot taken into account – a 3 star fix is still ( though quite accurate) is not really a fix but a best position indicator on a moving target – your position on this world.

And to keep this reasonably short – a 10 nm cocked hat was not an unreasonable achievement in a smooth air, well flown balanced aircraft – even if the bubble sextant was perfectly aligned. Remembering – in an P3B Orion between those 3 shots – with a 2 minute average – and 3 minutes between each shot – shot 1 at 0, shot 2 at 3 mins, shot 3 at 6 mins finishing at 8 mins and the aircraft is travelling at 6 nms per min – you are 48 nms away from the 1st shot starting point.

A succinct answer Josh 10 nms.

Regards HHG